3-D internal stress analysis is usually using the method of frozen stress and the method of light scattering. Aben proposed to vary the polarization state or the wavelength of incidence light in 1970. Then he could resolve the plane stress of each slab. But, we haven't got a satisfactory theory to obtain a method of measurement and analysis of S-D priciple stress yet. In this paper we expand the method of Aben and using it to the loaded plate model. Varying the wavelength of the incident light and measure the polarization character along each axis of y, z in combination with jnterferometric photoelesticity for a frozen stress medium. Then, using the analysis of this paper, we can provide for the information of the magnitude and direotion of three principle stress.